Experiment of December 23, 2017:

The time to submit an answer is over. You can now view the solution of the experiment.

Solution video:

Experiment:

Question:

What does Mr. Santa see, if he moves his finger from top to bottom between the postcard and the lamp?

A) The shadow of the finger appears down at the bottom of the card's core shadow, moving downwards.

B) The shadow of the finger emerges from below and moves into the core shadow of the card.

C) The shadow of the finger descends from above and moves into the core shadow of the card.

D) The shadow of the finger emerges up from the card's core shadow.

Advice of the day:

Please hold the postcard approximately 20-30 cm in front of the wall. The lamp should be a bit bigger (no point source) and be placed approximately 3 m away from the wall. Instead of one bigger lamp, you can also use several lamps next to each other. The one or two finger(s) move approximately 20-30 cm away from the postcard between the postcard and the lamp from top to bottom as shown in the movie.